Conveyor type sorters are widely used for the high speed separation of similar articles into two or more classes. The items are carried on a supply conveyor belt that passes through the sorter. The items are ejected or moved sideways on the belt into the desired catagories.
Where the items to be sorted are easily damaged such as agricultural produce or glass bottles, the items need to be separated gently in order to avoid bruising or breakage. One type of conveyor sorter for this purpose utilizes a roller chain belt moving parallel to the supply conveyor belt at substantially the same speed. The roller chain belt carried hundreds of pushers that move transversely over the supply conveyor belt when activated to push items on the belt. The sorting process utilized by these conveyor sorters includes determining what to do with the item, determining the position of an item on the supply conveyor, selecting a pusher or pushers to perform the sorting task, waiting until the pusher is in the proper position, extending the pusher, and retracting the pusher. Since the forward speeds of the item and the pusher are the same, the pusher is able to engage and push the item transversely for a relatively long period of time. The extension and retraction of the pusher is typically controlled by means of a cam guide that angles gently toward the supply conveyor and then away. Conveyor sorters having one or more of these characteristics are disclosed in U.S. Pat. Nos. 3,471,012; 3,771,648; 3,791,518; and 4,501,365.
Another device utilizing similar principles is disclosed in U.S. Pat. No. 2,609,926 entitled Bottle Sorting Machine. In this device, a turntable is positioned adjacent the supply conveyor belt on an axle perpendicular to the horizontal plane of the belt. Pushers on the turntable selectively move perpendicular to the axle to push bottles transversely on the supply conveyor belt. Each pusher has a forward lip for engaging the leading side of a bottle. The turntable is rotated thereby entirely due to the forward movement of the bottles on the supply conveyor belt. If a bottle is to be ejected, a solenoid starts the pusher for the bottle into an ejection cam guide.
Both the roller chain belt and turntable types of conveyor sorters have limitations. For example, the pusher roller chain belt devices have hundreds of parts changing direction with respect to each other at the ends of the chain belt causing noise and wear. The turntable device is able to operate against the pushed items only for a relatively short period of time due to the limited arc of the wheel in the usable position. An ejector means having a relatively long pusher operating time and no relative part movement except for that required to eject and retract a pusher would provide significant practical advantages.